• Suk Ho Sohn, Sihyun Chae, Jae Woong Choi, Karam Nam, Youn Joung Cho, Joo-Youn Cho, and Ho Young Hwang.
• Department of Thoracic and Cardiovascular Surgery, Seoul National University Hospital, Seoul National University College of Medicine, Seoul, Korea.
• J. Korean Med. Sci. 2024 Feb 26; 39 (7): e79e79.

BackgroundThis study evaluated the difference in brain metabolite profiles between normothermia and hypothermia reaching 25°C in humans in vivo.MethodsThirteen patients who underwent thoracic aorta surgery under moderate hypothermia were prospectively enrolled. Plasma samples were collected simultaneously from the arteries and veins to estimate metabolite uptake or release. Targeted metabolomics based on liquid chromatographic mass spectrometry and direct flow injection were performed, and changes in the profiles of respective metabolites from normothermia to hypothermia were compared. The ratios of metabolite concentrations in venous blood samples to those in arterial blood samples (V/A ratios) were calculated, and log2 transformation of the ratios [log2(V/A)] was performed for comparison between the temperature groups.ResultsTargeted metabolomics were performed for 140 metabolites, including 20 amino acids, 13 biogenic amines, 10 acylcarnitines, 82 glycerophospholipids, 14 sphingomyelins, and 1 hexose. Of the 140 metabolites analyzed, 137 metabolites were released from the brain in normothermia, and the release of 132 of these 137 metabolites was decreased in hypothermia. Two metabolites (dopamine and hexose) showed constant release from the brain in hypothermia, and 3 metabolites (2 glycophospholipids and 1 sphingomyelin) showed conversion from release to uptake in hypothermia. Glutamic acid demonstrated a distinct brain metabolism in that it was taken up by the brain in normothermia, and the uptake was increased in hypothermia.ConclusionTargeted metabolomics demonstrated various degrees of changes in the release of metabolites by the hypothermic brain. The release of most metabolites was decreased in hypothermia, whereas glutamic acid showed a distinct brain metabolism.© 2024 The Korean Academy of Medical Sciences.

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